The Somnambulist is a golem-like mute giant who subsists solely on milk, and his ancestry remains hidden. Loyal, mysterious, a tad slow on the draw, he nonetheless is indispensable to Moon. And now, together, the crime-fighting pair will face their last and greatest case.

A brace of identical murders sets off the fuse. Moon and the Somnambulist are plunged into a variety of seedy London milieus, from a traveling carnival to a particularly perverted whorehouse to the mucky banks of the Thames. Eerie figures pop up out of the fog like specters: Mr. Cribb, who claims to be as old as the city; Ned Love, who once knew the poet Coleridge; Arthur Barge, who begins courting Moon's housekeeper; Madame Innocenti, a medium who can really contact the dead. But just when the case seems ready to break open, in step the authorities.

Mr. Skimpole and Mr. Dedlock represent the Directorate, a secret branch of the government. They reveal to Moon that his murder cases are just the tip of a malign conspiracy that is intent on destroying the city. They force Moon to cooperate with them, and now things escalate from merely odd to seriously weird and deadly, with an imminent apocalypse looming.

Steampunk of a parodic sort

I'm a sucker for steampunk, and I found myself enjoying The Somnambulist as a reasonably credible instance of the genre. This is Barnes' first novel, and he does himself proud. With reservations expressed below, I'd place him in the Tim Powers/James Blaylock school, which takes a somewhat absurdist view of our ancestors. Despite a minor resemblance of protagonist, anyone expecting the elegant solemnity and gravitas of Christopher Priest's The Prestige (1995) will be disappointed. This is a book where characters, settings, emotions and themes are sketched in with the sparsest of linework, always with the intention of evoking a laugh. The villainy is comic-book, the bloody consequences—some killers named "the Prefects"—mere splatterpunk.

But not every steampunk book aspires to Gibson-Sterling levels. This one is more T.C. Boyle. Barnes employs the device of a very smart unreliable narrator who can zip the narrative along at frenetic levels. New characters are introduced about every three pages, as are new plot twists. The ultimate conspiracy has a certain admirable Chestertonian lunacy about it. And the coda is fully satisfying.

But a few quibbles remain. A pivotal relative of Moon's is introduced rather late in the game. Also, the Somnambulist himself remains a reactionary, albeit heroic cipher. His name makes a great title, but does his role actually merit the headline spot? Not really.

But the most unsettling thing about this book is that, ultimately, I don't believe Barnes takes the steampunk genre seriously. There's a fine line between humor and parody. The steampunk work of Blaylock and Powers, for instance, is full of humor, but empty of parody. They regard the Victorians as equals when contrasted with us 21st-century wise ones, just different. The concerns and loves and hates of our ancestors emerge as dramatically real. Barnes' cast and action, however diverting and entertaining, are always hovering on the edge of derision. If the past is another country, as the saying goes, an author must be careful not to mock overmuch the strange folkways of yore.